Current harmonic, current form factor and power factor modification unit for rectifier supplied loads

ABSTRACT

A device for connecting in series between a source of alternating current power and a direct current load which decouples the power flow from the source to the load and thereby enables efficient modification of the current waveform supplied by the source to reduce current harmonics, improve the current form factor and improve the power factor. Particular uses for the device include battery chargers, off-line switching power supplies as used by computers, electronic ballasts for fluorescent tubes and variable speed electric motor controls.

This application is a continuation of application Ser. No. 07/812,011,filed Dec. 23, 1991, now abandoned.

FIELD OF THE INVENTION

This invention relates to a device (and electrical power controlcircuitry therefore) for interposing between a source of alternatingelectric power and a direct current load so as to greatly reduce thepeak of current flow from the source and to substantially increase theduration of time that current flows from the source to the device andload in combination during each cycle of the source thereby reducing thesource current form factor and current harmonics and improving the powerfactor of the power supplied to the deuce and load in combination.

The device comprises a rectifier module, a current energy storagemodule, a current directing switch module, current and voltagetransducers and a control module to operate the current directing switchmodule in response to a number of inputs.

BACKGROUND OF THE INVENTION

The increasing use of battery chargers, switch mode power supplies forcomputers, electronic ballasts for fluorescent tubes, variable speedelectric motor controls and other similar equipment all have thepotential to dramatically increase the current waveform distortion ofpower generated by alternating current sources. These current waveformdistortions reduce the ability of a distribution system to transmitpower and cause conductive interference with other equipment connectedto the source.

Circuits for altering the characteristics of loads as seen by the sourceand thereby reduce the current waveform distortion have been known formany decades and have been widely used such as capacitors, inductors,synchronous capacitors, motor generator sets, ferroresonant transformersand filter and trap networks made up of these and other passive andactive components. The components of these circuits are bulky,cumbersome, expensive, noisy and in general are not responsive tochanges in the load requirements.

More recently, a number of prior art inventions have provided mechanismsfor providing unity power factor by using switching power supplysynchronisation to the input voltage waveform. These mechanisms have notspecifically addressed the problems of harmonics and form factor, havebeen electronically complex and make no provision for introduction ofoutside signals to alter the current wave form.

In particular, European Patent Application 218,267 first published Apr.15, 1987 by Kislowski uses a current signal derived from the output aswell as internal circulating current to obtain a control signal thusmaking for complexity and no mention is made of form factor orharmonics.

Wilkinson et al. in U.S. Pat. No. 4,677,366 issued Jun. 30, 1987 useseveral internal signals into very complex signal management circuitryto obtain unity power factor making no mention of form factor orharmonics.

Bucher in U.S. Pat. No. 4,683,529 issued Jul. 28, 1987 uses complexelectronic circuitry to obtain discontinuous or near discontinuouscurrent which necessitates the filtering circuitry mentioned in thereference. No mention is made of form factor or harmonics. By switchingbetween 0 and peak value currents with his system, the capability ofproviding significant RFI is generated as represented by his FIG. 8,neccessitating the complex filtering components of his FIG. 1.

Nowhere in the prior art is there found a device which in combination:

1) Limits the peak current to RMS value ratio,

2) Provides an in phase quasi sinusoidal current wave form,

3) Maintains virtually continuous current flow with

minimum range of variation,

thus providing improvements to the power factor, the current harmonics,current form factor and radio frequency interferance.

It is therefore an object of the invention to provide a means foraltering the waveform of the current flow to a rectifier fed directcurrent load which is less complex.

It is a further object of the invention to provide a means for alteringthe waveform of the current flow to a rectifier fed direct current loadwhich is less electronically and acoustically noisy and whereby loadintroduced disturbances into the power source are reduced.

It is a further object of the invention to provide a means for alteringthe waveform of the current flow to a rectifier fed direct current loadwhereby the power factor as seen by the power source is adjusted to moredesirable levels.

It is a further object of the invention to provide a means for alteringthe waveform of the current flow to a rectifier fed direct current loadwhereby the harmonic content of the current supplied by the power sourceis adjusted to more desirable levels.

It is a further object of the invention to provide a means for alteringthe waveform of the current flow to a rectifier fed direct current loadwhereby the form factor of the current supplied by the power source isadjusted to more desirable levels.

It is a further object of the invention to provide a means for alteringthe waveform of the current flow to a rectifier fed direct current loadwhereby the load has increased isolation from power source disturbances.

It is a further object of the invention to provide a means for alteringthe waveform of the current flow to a rectifier fed direct current loadwhich is responsive to changes in other loads

Further and other objects of the invention will be apparent to thoseskilled in the art from the following Summary of the Invention andDescription of a Preferred Embodiment of the Invention

SUMMARY OF THE INVENTION

According to one aspect of the invention there is provided an apparatusfor connecting in series between a source of alternating currentelectrical power and a direct current load for decoupling the flow ofpower from the source to the load with said decoupling being arranged tomaintain desired parameters of power flow such as current form factor,current harmonics, and power factor, to the combined device and load;such apparatus comprising;

(a) electrical connector means for interposing the apparatus between thecurrent carrying components of the source and the load;

(b) an electric power rectifier to convert the current flow fromalternating to direct;

(c) a current energy storage network to enable decoupling of the loadfrom the source;

(d) an electrical power switching network to direct the flow of energyamong the source, said current energy storage network and the load;

(e) at least one current sensor to provide signals concerning sourcecurrent flow;

(f) at least one voltage sensor to provide signals concerning sourcevoltage levels;

(g) electrical means responsive to said sensor signals which convertsthese said signals into control signals for said electrical switchnetwork so as to maintain desired parameters of power flow from thesource.

According to another aspect of the invention there is provided anapparatus for connecting in series between a source of rectifiedalternating current electrical power and a direct current load fordecoupling the flow of power from the source to the load with saiddecoupling being arranged to maintain desired parameters of power flowsuch as current form factor, current harmonics, and power factor, to thecombined device and load, such apparatus being in combination;

(a) electrical connector means for interposing the apparatus between thecurrent carrying components of the source and the load;

(b) a current energy storage network to enable decoupling of the loadfrom the source;

(c) an electrical power switching network to direct the flow of energyamong the source, said current energy storage network and the load;

(d) at least one current sensor to provide signals concerning sourcecurrent flow;

(e) at least one voltage sensor to provide signals concerning sourcevoltage levels;

(f) electrical means responsive to said sensor signals which convertsthese said signals into control signals for said electrical switchnetwork so as to maintain desired parameters of power flow from thesource.

According to yet another aspect of the invention, a device is providedfor being connected in series between a source of electric power and adirect current load (for example, the input filter capacitor of anelectronic ballast for a fluorescent lamp), comprising;

(I) a series electrical power circuit comprising;

(a) an electrical connector, such as one side of a male plug, for makingthe connection of one side of an electrical power supply to

(b) one of the A.C. input nodes of an electrical power rectifier module,such as four power diodes connected as a full wave bridge having firstand second A.C. input nodes and a D.C. positive node and a D.C. negativenode, with the D.C. positive node of the electrical power rectifierconnected to

(c) one side of a current energy storage module, such as an inductor,whose other side is connected to the current input terminal of a currentswitch module such terminal being both

(d)(1) the current input side of a current switch, such as the drainterminal of a field effect power transistor, the current output side ofsaid current switch, which is also the storage current output terminalof said current switch module, such as the source terminal of said fieldeffect power transistor, which is connected to the first side of acurrent transducer module for providing an instantaneous measure ofcurrent which is the rectified source line current and

(d)(2) one side of a unidirectional switch, such as the anode side of apower diode, the second side of said unidirectional switch, such as thecathode side of said power diode, which is the load current outputterminal of the current switch module, is connected to

(e) the positive node of a load, such as the input filter capacitor ofan electronic fluorescent ballast, the negative node of which is in turnalso connected to the first side of said current transducer module

(f) making both the second side of said current switch and said negativenode of the load connected to the first side of said current transducermodule, such as one side of a very low value resistor, the second sideof which is connected to the D.C. negative node of said electrical powerrectifier

(f) continuing via said electrical power rectifier to the other A.C.input node which is connected to

(g) an electrical power connector, such as the other side of said maleplug, for finally making connection to the other side of the electricalpower supply and

(II) a switch control module consisting of;

(a) a first sensing circuit network, connected to said currenttransducer module, for providing a first electrical signal, such as avoltage, that is a measure of current flowing from the electrical powersource, said sensing circuit network provides differing electricalsignals (voltages) corresponding to when said current switch is off, on,and the instantaneous level of current flow from the source, and

(b) a second sensing circuit network, connected to said D.C. positivenode of said electrical power rectifier, for providing a secondelectrical signal, such as a voltage, that is a positive instantaneousmeasure of the voltage of the electrical power source, and

(c) an electrical switch control network which takes :said first andsecond electrical signals and converts them, as is appropriate, into adigital "1'" or "0'" which is connected to the control terminal of saidcurrent switch, such as the gate terminal of said field effect powertransistor thereby turning on or off said current switch, such a networkin one embodiment constructed using a comparator integrated circuit andassociated resistors.

According to a further aspect of the invention, a device is provided forbeing connected in series between a source of electric power and adirect current load (for example, the input filter capacitor of anelectronic ballast for a fluorescent lamp):, comprising;

(I) a series electrical power circuit comprising;

(a) an electrical connector, such as one side of a male plug, for makingthe connection of one side of an electrical power supply to

(b) one of the A.C. input nodes of an electrical power rectifier module,such as four power diodes connected as a full wave bridge having firstand second A.C. input nodes and a D.C. positive node and a D.C. negativenode, with the D.C. positive node of the electrical power rectifierconnected to

(c) one side of a current energy storage module, such as an inductor,whose other side is connected to the current input terminal of a currentswitch module such terminal being both

(d)(1) the current input side of a current switch, such as the drainterminal of a field effect power transistor, the current output side ofsaid current switch, which is also the storage current output terminalof said current switch module, such as the source terminal of said fieldeffect power transistor, which is connected to the first side of acurrent transducer module for providing an instantaneous measure ofcurrent which is the rectified source line current and

(d)(2) one side of a unidirectional switch, such as the anode side of apower diode, the second side of said unidirectional switch, such as thecathode side of said power diode, which is the load current outputterminal of the current switch module, is connected to

(e) the positive node of a load, such as the input filter capacitor ofan electronic fluorescent ballast, the negative node of which is in turnalso connected to the first side of said current transducer module

(f) making both the second side of said current switch and said negativenode of the load connected to the first side of said current transducermodule, such as one side of a very low value resistor, the second sideof which is connected to the D.C. negative node of said electrical powerrectifier

(f) continuing via said electrical power rectifier to the other A.C.input node which is connected to

(g) an electrical power connector, such as the other side of said maleplug, for finally making connection to the other side of the electricalpower supply and

(II) a switch control module consisting of;

(a) a first sensing circuit network, connected to said currenttransducer module, for providing a first electrical signal, such as avoltage, that is a measure of current flowing from the electrical powersource, said sensing circuit network provides differing electricalsignals (voltages) corresponding to when said current switch is off, on,and the instantaneous level of current flow from the source, a sensingcircuit network in one embodiment being constructed using an operationalamplifier integrated circuit and associated resistors and

(b) a second sensing circuit network, connected to said D.C. positivenode of said electrical power rectifier, for providing a secondelectrical signal, such as a voltage, that is a positive instantaneousmeasure of the voltage of the electrical power source, a sensing circuitnetwork in one embodiment being constructed using an operationalamplifier integrated circuit and associated resistors, and

(c) a third sensing circuit network, connected to said positive node ofthe load, for providing a third electrical signal, such as a voltage,that is a measure of the positive instantaneous voltage of the load,such a sensing circuit network in one embodiment being constructed usingan operational amplifier integrated circuit and associated resistors,and

(d) an electrical signal processing network which takes said first,second, and third electrical signals and converts them, as isappropriate, into a digital "1'" or "0'" which is connected to thecontrol terminal of said current switch, such as the gate terminal ofsaid field effect power transistor thereby turning on or off saidcurrent switch, such a network in one embodiment constructed using acomparator integrated circuit and associated resistors.

According to still yet another aspect of the invention, a device isprovided for being connected in series between a source of electricpower and the input filter capacitor of an electronic ballast for afluorescent lamp, comprising;

(I) a series electrical power circuit comprising;

(a) an electrical connector, such as one side of a male plug, for makingthe connection of one side of an electrical power supply to

(b) one of the A.C. input nodes of an electrical power rectifier, suchas four power diodes connected as a full wave bridge having first andsecond A.C. input nodes and a D.C. positive node and a D.C. negativenode, with the D.C. positive node of the electrical power rectifierconnected to

(c) one side of an inductor, whose other side is connected to thecurrent input node of a current switch module such node being connectedto both

(d)(1)an input terminal of a current switch, such as the drain terminalof a field effect power transistor, whose output terminal, such as saidtransistor's source terminal, is connected to the first side of acurrent measuring low value resistor

(d)(2) the anode side of a power diode, the cathode side of which isconnected to

(e) the positive node of the input filter capacitor of an electronicfluorescent ballast, the negative node of which is in turn alsoconnected to the first side of said current measuring low voltage valueresistor

(f) making both the switch output terminal and the negative node of theload connected to the first side of the low value resistor, the secondside of which is connected to the D.C. negative node of said electricalpower rectifier

(f) continuing via said electrical power rectifier to the other A.C.input node which is connected to

(g) an electrical power connector, such as the other side of said maleplug, for finally making connection to the other side of the electricalpower supply and

(II) a switch control module consisting of;

(a) a first sensing circuit network, connected to said current measuringresistor, for providing a first electrical signal, such as a voltage,that is a measure of current flowing from the electrical power source,said sensing circuit network provides differing electrical signals(voltages) corresponding to when said current switch is off, on, and theinstantaneous level of current flow from the source, a sensing circuitnetwork in one embodiment being constructed using an operationalamplifier integrated circuit and associated resistors and

(b) a second sensing circuit network, connected to said D.C. positivenode of said electrical power rectifier, for providing a secondelectrical signal, such as a voltage, that is a positive instantaneousmeasure of the voltage of the electrical power source, a sensing circuitnetwork in one embodiment being constructed using an operationalamplifier integrated circuit and associated resistors, and

(c) a third sensing circuit network, connected to said positive node ofthe load, for providing a third electrical signal, such as a voltage,that is a measure of the positive instantaneous voltage of the load,such a sensing circuit network in one embodiment being constructed usingan operational amplifier integrated circuit and associated resistors,and

(d) an electrical signal processing network which takes said first,second, and third electrical signals and converts them, as isappropriate, into a digital "1'" or "0'" which is connected to thecontrol terminal of said current switch, such as the gate terminal ofsaid field effect power transistor thereby turning on or off saidcurrent switch, such a network in one embodiment constructed using acomparator integrated circuit and associated resistors. In analternative embodiment the current switch is a bipolar transistorpreferably which may have an isolated base.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system and functional block diagram of a device constructedaccording to a preferred embodiment of the invention.

FIG. 2 is a drawing of the electrical circuit of a preferred embodimentof the invention shown in FIG. 1 including connection to a source ofalternating current electrical power and the input capacitor of a directcurrent load.

FIG. 3 is a representation of the voltage and current waves of a sourceof alternating current power during normal device operation.

FIG. 4 is a drawing of a preferred embodiment of the invention shown inFIG. 1 incorporating safety overvoltage feature and provision for inputof an outside signal.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

In its system and functional block diagram embodiment the presentinvention includes, as shown in FIG. 1, electrical means for connectingto the commercial power supply, a rectifier module, a current energystorage module, a current switch module, electrical means for connectingto a direct current load, electrical supply current and voltagetransducers, and a switching control module. These elements function asa system to decouple the power flow from the electric power source tothe load so as to allow desirable management of current flows from thesource.

A detailed circuit configuration of an embodiment of the invention willnow be described in conjunction with FIGS. 1 and 2.

The circuit consists of two principal parts; the first, a seriesconnected electrical power circuit, which performs the functions ofconnecting to the power supply and to the load, performing therectification to direct current, and regulating the flow of current tothe load; the second, an electronic switching control circuit, whichperforms the functions of sensing the flow of current from the powersupply, sensing the instantaneous voltage of the power supply, sensingthe instantaneous voltage of the load input, combining and convertingthese sensed signals into reference and level signals to a comparatorwhose output controls the current regulating function of the powercircuit.

The power circuit is connected via electrical means, such as a firstmale blade 10 of a plug, to one side of the power supply 1 which is thecommercially available electricity supply at 120 volts 60 Hertz. Inseries with blade 10 is one alternating current terminal, node 201, of 2ampere bridge rectifier 2. The positive direct current terminal of 2,node 202, is connected to the first side of the 1 millihenry, 1 ampereinductor 3. The second side of 3, node 203, is connected to both theanode side of 2 ampere diode 4 and the drain terminal of power fieldeffect transistor 5, being type IRF722. The cathode side 4, node 204, isconnected to both the positive terminal of the 250 microfarad filtercapacitor 6 and the positive terminal of the electronic fluorescentballast, represented by the non-linear impedance 7. The negative side of6 and 7, node 205, is connected to both the drain terminal of 5 and oneside of 5.6 ohm resistor 9. The other side of 9, node 206, is connectedto the negative direct current terminal of 2. The other alternatingcurrent terminal of 2 completes the power circuit via a second maleblade 11 of said plug to power supply 1.

The switching control circuit begins with a line current sensing networkconsisting of 10,000 ohm resistor 16, 100,000 ohm resistor 17 and 100picofarad resistor 32. This network divides approximately by 0.9 and isa 0.1 microsecond noise filter of the signal at node 205, which is now apositive instantaneous analog of current flowing from power supply 1.This analog is presented at node 210 to the negative input of comparator25, being 1/4 of a dual/dual amplifier-comparator integrated circuit asmanufactured by Motorola Inc. as part number MC14575. The next networkis a reference network made up of a base voltage obtained by dividingthe electronic power supply 30 voltage (+9 volts) by a voltage dividermade up of 240,000 ohm resistor 34, and 10,000 ohm resistor 35, modifiedby a signal from node 202 via 1,000,000 ohm resistor 33 to establish areference at node 215. This reference is further modified by thehysteresis feedback of the comparator output through 1,500,000 ohmresistor yielding a signal of approximately [+0.360+1.70|sin377t|±0.06]volts connected to the non-inverting (+) terminal ofcomparator 25.

The switching control consists of comparator 25 and 47 ohm resistor 29.The output of comparator 25 drives the gate terminal of transistor 5through resistor 29 in the positive direction to approximately +9 voltswhen voltage at node 210, is less than node 215 and to 0 volts when node210 is more than node 215.

The operation of the invention as embodied in the circuit of FIG. 2 willnow be more particularly described in conjunction with FIG. 3.

Assume that supply 30 is powered, the voltage wave of source 1 is atzero commencing a positive excursion, no current is flowing and there isno voltage at node 204. In this state switch 5 will be turned on becausenode 215 will be higher than node 210. As the source voltage Vincreases, current will flow through 3, 5, and 9, rising in value atapproximately a rate of 1000×VA.C. amperes per second. In approximately50 microseconds, when the current reaches a value of approximately 85milliamperes, the voltage level at node 210 exceeds that of node 215 andthe comparator 25 turns switch 5 off. At this early stage of the voltagewave, approximately 1.5 volts, the effect of the voltage at node 202 isnegligible. The energy stored in 3 by the flow of current in 3 is nowavailable to charge the capacitor 6 by instituting a current flowthrough diode 4. This causes a decrease of current in 3 andsimultaneously in 9. In approximately 1 microsecond the energy istransferred to the capacitor as the current decreases to approximately60 milliamperes and the comparator 25 turns 5 on again and the switchingcycle begins again. As the voltage of the supply increases, theinfluence of the voltage at node 215 increases and ever increasinglevels of current in the power circuit are required to bring node 210 toa higher level than node 215 thus switching 5 off and, simultaneously,the level of current at which 5 switches back on again increases. At thepeak of the voltage wave the observed current level is approximately 440milliamps at peak and 280 milliamps at valley with a switch closed time(rising current, energy storage) of approximately 2 microseconds and aswitch open time (energy transfer, falling current) of approximately 6microseconds. Similarly as the supply voltage decreases ever decreasinglevels of current are required to cause switch 5 to transfer. When thesource goes through the negative half of its voltage cycle, the actionof the rectifier causes node 202 to go through another positive cycleand the switching cycles of 5 are as described previously with the samecurrent flows and energy transfers. The nature of the energy transferout of the inductor into the capacitor is such that it will generatevoltage as is required to transfer energy into the capacitor and henceto the load. By examining FIG. 3 with regard to the shape of the currentand the phase relationship of the current to the voltage it can be seenthat the current is virtually continuous, of approximately sinusoidalshape and in phase with the voltage wave. Thus the device provides aload which behaves approximately resistive with a high frequencysawtooth superimposed upon it.

A detailed circuit configuration of an embodiment of the invention willnow be described in conjunction with FIG. 4.

The circuit consists of two principal parts; the first, a seriesconnected electrical power circuit, which performs the functions ofconnecting to the power supply and to the load, performing therectification to direct current, and regulating the flow of current tothe load; the second, an electronic sensing and switching controlcircuit, which performs the functions of sensing the flow of currentfrom the source of electrical power, sensing the instantaneous voltageof the source, as a safety feature, sensing the instantaneous voltage ofthe load input, providing an input for external signals, combining andconverting these sensed signals into reference and level signals to acomparator whose output controls the current management function of thepower circuit.

The power circuit is connected via electrical means, such as a firstmale blade 10 of a plug, to one side of the power supply 1 which is thecommercially available electricity supply at 120 volts 60 Hertz. Inseries with blade 10 is one alternating current terminal, node 201, of 2ampere bridge rectifier 2. The positive direct current terminal of 2,node 202, is connected to the first side of the 1 millihenry, 1 ampereinductor 3. The second side of 3, node 203, is connected to both theanode side of 2 ampere diode 4 and the drain terminal of power fieldeffect transistor 5, being type IRF722. The cathode side 4, node 204, isconnected to both the positive terminal of the 250 microfarad filtercapacitor 6 and the positive terminal of the electronic fluorescentballast, represented by the non-linear impedance 7. The negative side of6 and 7, node 205, is connected to both the drain terminal of 5 and oneside of 1.25 ohm resistor 8. The other side of 8, node 206, is connectedto the negative direct current terminal of 2. The other alternatingcurrent terminal of 2 completes the power circuit via a second maleblade 11 of said plug to power supply 1.

The electronic sensing and switching control circuit begins with a linecurrent and voltage sensing network consisting of operational amplifier12, being 1/4 of a dual/dual amplifier-comparator integrated circuit asmanufactured by Motorola Inc. as part number MC14575, 10,000 ohmresistor 13, 150,000 ohm resistor 14, 5,400,000 ohm resistor 15, 10,000ohm resistor 16, and 100,000 ohm resistor 17. This network initiallyamplifies the voltage signal at node 205, representing the currentflowing from power supply 1, with a gain of approximately 15 establishedby the ratio of resistors 14/13 at node 210. In addition, superimposedon the current signal at node 210 by subtraction is the voltage at node202 multiplied by the gain factor of approximately 0.019 established bythe ratio of resistors 14/15. Finally, it is possible to introducingsuitably buffered signals at node 208 which further modify the thesignal at node 210 in order to cause other desired changes in theoperation of the device such as complimentarily offsetting the currentwaveshape of a second different load thereby improving the power factorand other parameters of the combined system.

The next network is a load voltage sensing network consisting ofoperational amplifier 18, being another 1/4 of said amplifier-comparatorintegrated circuit, 1,500,000 ohm resistor 19, 20,000 ohm resistor 20,100,000 ohm resistor 21, 10,000, ohm resistors 23 & 24 and 10,000,000ohm resistor 22. The principal function of this load voltage sensingnetwork is to provide a safety limit to the voltage at node 204 to avalue that will not overstress circuit components in the event of lossof load such as the tube being removed in an electronic fluorescentballast. This network does not normally take part in the operation ofthe invention. By sensing the load voltage level at node 204 the networkis arranged to reduce the voltage at node 214 very rapidly to a lowlevel, typically less than 0.2 volts, whenever the voltage at node 204exceeds approximately 350 volts. A brief description of the networkoperation is as follows. The electronic power supply 30 voltage (+9volts) is divided by a voltage divider made up of resistors 23 & 24 toestablish a reference at node 213. This reference (+4.5 volts) isconnected to the non-inverting (+) terminal of operational amplifier 18.The load voltage at node 204 is divided at node 211 by a voltage dividermade up of resistors 19 & 20 to a ratio of approximately 0.013. Node 211is connected via resistor 21 to the inverting (-) terminal ofoperational amplifier 18, node 212. This node 212 is also connected toone side of resistor 22 the other side of which is connected to theoutput terminal of 18, node 214. The effect of this network is to havethe voltage at node 214 be virtually at electronic power supply 30voltage (approx. +9 volts) whenever the voltage at node 204 is less thanapproximately 335 volts and node 214 to be at less than 0.2 voltswhenever node 204 is greater than approximately 350 volts.

The switching control network consists of comparator 25 being a third1/4 of said amplifier-comparator integrated circuit, 240,000 ohmresistor 26, 36,000 ohm resistor 27, 1,500,000 ohm resistor 28 and 47ohm resistor 29. This network operates using as reference the voltage atnode 215 of approximately 1.25 volts which, in normal operation, is madeup of the voltage at node 214 divided by the ratio of 26/27 modified bythe feedback of 28 to provide approximately 0.2 volts of hysteresisbetween when the comparator 25 output is high (+9 volts) and low (0volts). The output of comparator 25 now drives the gate terminal oftransistor 5 through resistor 29 in the positive direction toapproximately +9 volts when the output voltage of the line current andvoltage sensing network, node 210, is less than node 215 and to 0 voltswhen node 210 is more than node 215.

The operation of the invention as embodied in the circuit of FIG. 4 willnow be more particularly described in conjunction with FIG. 3.

Assume that supply 30 is powered, the voltage wave of source 1 is atzero commencing a positive excursion, no current is flowing and there isno voltage at node 204. In this state switch 5 will be turned on becausenode 215 will be higher than node 210. As the source voltage Vincreases, current will flow through 3, 5, and 8, rising in value atapproximately a rate of 1000×VA.C. amperes per second. In approximately50 microseconds when the current reaches a value of approximately 65milliamperes, the voltage level at node 210 exceeds that of node 215 andthe comparator 25 turns switch 5 off. At this early stage of the voltagewave, approximately 1.5 volts, the effect of the voltage at node 202 isnegligible. The energy stored in 3 by the flow of current in 3 is nowavailable to charge the capacitor 6 by instituting a current flowthrough diode 4. This causes a decrease of current in 3 andsimultaneously in 8. In approximately 1 microsecond the energy istransferred to the capacitor as the current decreases to approximately60 milliamperes and the comparator 25 turns 5 on again and the switchingcycle begins again. As the voltage of the supply increases, theinfluence of the voltage at node 202 increases and ever increasinglevels of current in the power circuit are required to bring node 210 toa higher level than node 215 thus switching 5 off and, simultaneously,the level of current at which 5 switches back on again increases. At thepeak of the voltage wave the the current level is approximately 440milliamps at peak and 280 milliamps at valley with a switch closed time(rising current, energy storage) of approximately 2 microseconds and aswitch open time (energy transfer, falling current) of approximately 6microseconds. Similarly as the supply voltage decreases ever decreasinglevels of current are required to cause switch 5 to transfer. When thesource goes through the negative half of its voltage cycle, the actionof the rectifier causes node 202 to go through another positive cycleand the switching cycles of 5 are as described previously with the samecurrent flows and energy transfers. The nature of the energy transferout of the inductor into the capacitor is such that it will generatevoltage as is required to transfer energy into the capacitor and henceto the load. By examining FIG. 3 with regard to the shape of the currentand the phase relationship of the current to the voltage it can be seenthat the current is both in phase with the voltage wave and ofapproximately sinusoidal shape. This provides a load which appearsapproximately resistive with a high frequency sawtooth superimposed uponit.

When an input power of 120 volts 60 hertz was connected to either of theembodiments described and load of a 30 watt electronic fluorescentballast in combination was measured, the power factor was approximately+97 percent, the current form factor was approximately 1.6, and the 3rd,5th, 7th, 9th, 11th, and 13th harmonics of current were all less than 4percent with a total harmonic distortion of current of less than 7percent. By comparison, the same load connected directly to the sourcehad power factor of approximately -48 percent, form factor approximately3.6 and total harmonic distortion approximately 170 percent.

By removing the network connected between nodes 202, 204, 205, 206, and217 of FIG. 4 and replacing it with one that varied the switching of 5in accordance with other algorithms in response to the inputs, otherfactors regarding the shape of the current wave could be implemented.For example, by altering the phase relationship of the current wave to"lead" the voltage wave, the load could now be used for power factorcorrection. In another variation, an additional input could beincorporated into the device to cause the current waveshape tocomplimentarily offset the current waveshape of a second different loadthereby improving the power factor and other parameters of the combinedsystem.

As many changes can be made to the embodiment of the invention withoutdeparting from the scope of the invention, it is intended that allmaterial be considered as illustrative of the invention and not in alimiting sense.

The embodiments of the invention in which an exclusive property orprivilege is claimed are as follows:
 1. A device is provided for beingconnected in series between a source of electric power and a directcurrent load (for example, the input filter capacitor of an electronicballast for a fluorescent lamp), comprising;(I) a series electricalpower circuit comprising;(a) an electrical connector, such as one sideof a male plug, for making the direct connection of one side of anelectrical power supply to (b) one of the A.C. input nodes of anelectrical power rectifier module connected with the electricalconnector means, such as four power diodes connected as a full wavebridge having first and second A.C. input nodes and a D.C. positive nodeand a D.C. negative node, with the D.C. positive node of the electricalpower rectifier connected to (c) one side of a current energy storagemodule connected with a direct current terminal of the electric powerrectifier module, such as an inductor, whose other side is connected tothe current input terminal of a current switch module for controllingthe source current and connected with the current energy storage networksuch terminal being both (d)(1) the current input side of a currentswitch, such as the drain terminal of a field effect power transistor,the current output side of said current switch, which is also thestorage current output terminal of said current switch module, such asthe source terminal of said field effect power transistor, which isconnected to the first side of a current transducer module for providingan instantaneous measure of current which is the rectified source linecurrent and (d)(2) one side of a unidirectional switch, such as theanode side of a power diode, the second side of said unidirectionalswitch, such as the cathode side of said power diode, which is the loadcurrent output terminal of the current switch module, is connected to(e) the positive node of a load, such as the input filter capacitor ofan electronic fluorescent ballast, the negative node of which is in turnalso connected to the first side of said current transducer module(f)(1) making both the second side of said current switch and saidnegative node of the load connected to the first side of said currenttransducer module, such as one side of a very low value resistor, thesecond side of which is connected to the D.C. negative node of saidelectrical power rectifier (f)(2) continuing via said electrical powerrectifier to the other A.C. input node which is connected to (g) anelectrical power connector, such as the other side of said male plug,for finally making connection to the other side of the electrical powersupply and (II) a switch control module consisting of;(a) a firstsensing circuit network, connected to said current transducer module,for providing a first electrical signal, such as a voltage, that is ameasure of AC current flowing from the electrical power source, saidsensing circuit network provides differing electrical signals (voltages)corresponding to when said current switch is off, on, and theinstantaneous level of AC current flow from the source, and (b) a secondsensing circuit network, connected to said D.C. positive node of saidelectrical power rectifier, for providing a second electrical signal,such as a voltage, that is a positive instantaneous measure of thevoltage of the electrical power source, and (c) an electrical switchcontrol network which takes only said first and second current andvoltage electrical signals and converts them, as is appropriate, into adigital "1'" or "0'" which is connected to the control terminal of saidcurrent switch, such as the gate terminal of said field effect powertransistor thereby turning on or off said current switch.
 2. Apparatusfor connecting in series between a source of alternating currentelectrical power and a direct current load for decoupling the flow ofpower from the source to the load with said decoupling being arranged tomaintain desired parameters of power flow such as current form factor,current harmonics, and power factor, to the combined device and loadsuch apparatus being in combination;(I) a series electrical powercircuit comprising;(a) an electrical connector, such as one side of amale plug, for making direct connection of one side of an electricalpower supply to (b) one of the A.C. input nodes of an electrical powerrectifier module connected with the electrical connector means, such asfour power diodes connected as a full wave bridge having first andsecond A.C. input nodes and a D.C. positive node and a D.C. negativenode, with the D.C. positive node of the electrical power rectifierconnected to (c) one side of a current energy storage module connectedwith a direct current terminal of the electric power rectifier module,such as an inductor, whose other side is connected to both (d)(1) thecurrent input side of a current switch for controlling the sourcecurrent and connected with the current energy storage network, such asthe drain terminal of a field effect power transistor, the currentoutput side of said current switch, such as the source side of saidfield effect power transistor, which is connected to the first side of acurrent transducer module for providing an instantaneous measure ofcurrent which is the rectified source line current and (d)(2) one sideof a unidirectional switch, such as the anode side of a power diode, thesecond side of said unidirectional switch, such as the cathode side ofsaid power diode, is connected to (e) the positive node of a load, suchas the input filter capacitor of an electronic fluorescent ballast, thenegative node of which is in turn also connected to the first side ofsaid current transducer module (f)(1) making both the second side of thecurrent switch and the negative node of the load connected to the firstside of said current transducer module, such as one side of a very lowvalue resistor, the second side of which is connected to the D.C.negative node of the said electrical power rectifier (f)(2) continuingvia said electrical power rectifier to the other A.C. input node whichis connected to (g) an electrical power connector, such as the otherside of said male plug, for finally making connection to the other sideof the electrical power supply and (II) an electronic sensing and switchcontrol module consisting of;(a) a first sensing circuit network,connected to said current transducer module, for providing a firstelectrical signal, such as a voltage, that is a measure of AC currentflowing from the electrical power source, said sensing circuit networkprovides differing electrical signals (voltages) corresponding to whensaid current switch is off, on, and the instantaneous level of ACcurrent flow in the supply, and (b) a second sensing circuit network,connected to said D.C. positive node of said electrical power rectifier,for providing a second electrical signal, such as a voltage, that is ameasure of the positive instantaneous voltage of the electrical powersource, and (d) an electrical signal processing network which takes onlysaid first, and second, current and voltage electrical signals andconverts them, as is appropriate, into a digital "1'" or "0'" which isconnected to the control terminal of said current switch, such as thegate terminal of said field effect power transistor thereby turning onor off said current switch.
 3. The combination defined in claim 2,wherein the current switch is a bipolar power transistor.
 4. Thecombination defined in claim 2, wherein the current switch is anisolated base bipolar power transistor.
 5. An apparatus for connectingin series between a source of alternating current electrical power andthe input filter capacitor of an electronic ballast for a fluorescentlamp for decoupling the flow of power from the source to the load withsaid decoupling being arranged to maintain desired parameters of powerflow such as current form factor, current harmonics, and power factor,to the combined device and electronic ballast such apparatus being incombination;(I) a series electrical power circuit comprising;(a) anelectrical connector, such as one side of a male plug, for making directconnection of one side of an electrical power supply to (b) one of theA.C. input nodes of an electrical power rectifier connected with theelectrical connector means, such as four power diodes connected as afull wave bridge having first and second A.C. input nodes and a D.C.positive node and a D.C. negative node, with the D.C. positive node ofthe electrical power rectifier connected to (c) one side of an inductor,whose other side is connected to the current input node of a currentswitch module for controlling the source current and connected with thecurrent energy storage network, such node being connected to both (d)(1)an input terminal of a current switch, such as the drain terminal of afield effect power transistor, whose output terminal, such as saidtransistor's source terminal, is connected to the first side of acurrent measuring low value resistor (d)(2) the anode side of a powerdiode, the cathode side of which is connected to (e) the positive nodeof the input filter capacitor of an electronic fluorescent ballast, thenegative node of which is in turn also connected to the first side ofsaid current measuring low voltage value resistor (f)(1) making both theswitch output terminal and the negative node of the load connected tothe first side of the low value resistor, the second side of which isconnected to the D.C. negative node of said electrical power rectifier(f)(2) continuing via said electrical power rectifier to the other A.C.input node which is connected to (g) an electrical power connector, suchas the other side of said male plug, for finally making connection tothe other side of the electrical power supply and (II) a switch controlmodule consisting of;(a) a first sensing circuit network, connected tosaid current measuring resistor, for providing a first electricalsignal, such as a voltage, that is a measure of AC current flowing fromthe electrical power source, said sensing circuit network providesdiffering electrical signals (voltages) corresponding to when saidcurrent switch is off, on, and the instantaneous level of AC currentflow from the source, and (b) a second sensing circuit network,connected to said D.C. positive node of said electrical power rectifier,for providing a second electrical signal, such as a voltage, that is apositive instantaneous measure of the voltage of the electrical powersource, a sensing circuit network in one embodiment being constructedusing an operational amplifier integrated circuit and associatedresistors, and (d) an electrical signal processing network which takesonly said first, and second, current and voltage electrical signals andconverts them, as is appropriate, into a digital "1'" or "0'" which isconnected to the control terminal of said current switch, such as thegate terminal of said field effect power transistor thereby turning onor off said current switch.
 6. The combination defined in claim 5,wherein the current switch is a bipolar power transistor.
 7. Thecombination defined in claim 5, wherein the current switch is anisolated base bipolar power transistor.